A power system is known (for example, JP-A-H05-278483) which includes an electric motor, a differential gear system that distributes output power of the electric motor to a left wheel and a right wheel, and a parking mechanism (rotation restricting mechanism) that is disposed on power transmission paths between the electric motor and the left wheel and the electric motor and the right wheel. This type of power system is provided as a front wheel drive system or a rear wheel drive system in an electric motor vehicle such as a hybrid vehicle or an electric vehicle, and it is desired to reduce size and weight while maintaining an appropriate power transmission function.
In the power system disclosed in JP-A-H05-278483, however, since a parking gear is provided in the differential gear casing of the differential gear system, there are problems that the parking mechanism makes a force for maintaining wheels, that is, a vehicle large in a stop state and the parking mechanism increases in size.
The invention is to provide a power system in which a rotation restricting mechanism can make a force for maintaining wheels small in a stop state and the rotation restricting mechanism can be reduced in size.
The invention provides following aspects (1) to (5).
(1) A power system (e.g., a power system 1 in an embodiment) including:
an electric motor (e.g., an electric motor 2 in an embodiment) that drives a left wheel and a right wheel of a vehicle;
a transmission (e.g., a transmission 5 in an embodiment) that is disposed on power transmission paths between the electric motor and the left wheel (e.g., a left wheel LW in an embodiment) and between the electric motor and the right wheel (e.g., a right wheel RW in an embodiment); and
a differential gear system (e.g., a differential gear system 6 in an embodiment) that distributes output power shifted by the transmission to the left wheel and the right wheel, wherein:
the transmission includes
a first gear (e.g., a first gear 51 in an embodiment) that is mechanically connected to the electric motor,
a second gear (e.g., a second gear 52 in an embodiment) that has a rotation axis in common with the first gear and is mechanically connected to a differential gear casing (e.g., a differential gear casing 61 in an embodiment) of the differential gear system, and
a plurality of pinion gears (e.g., pinion gears 53 in an embodiment) that mesh with the first gear and the second gear;
the plurality of pinion gears are supported to be capable of rotating and not to be capable of revolving;
one pinion gear out of the plurality of pinion gears is only mechanically connected to a rotation restricting mechanism (e.g., a rotation restricting mechanism 70 to be described below) that is switchable between an operating state and a non-operating state; and
the rotation restricting mechanism restricts rotation of the pinion gear in the operating state, and permits the rotation of the pinion gear in the non-operating state.
(2) The power system according to (1), wherein
the one pinion gear is located at an uppermost position out of the plurality of pinion gears.
(3) The power system according to (1) or (2), wherein
the pinion gear includes a large diameter gear (e.g., a large diameter gear 53a in an embodiment) and a small diameter gear (e.g., a small diameter gear 53b in an embodiment), and
the small diameter gear meshes with the second gear.
(4) The power system according to (3), wherein
the large diameter gear of the one pinion gear has a parking gear (e.g., a parking gear 53d to be described below) engaged with the rotation restricting mechanism.
(5) The power system according to any one of (1) to (4), wherein
an actuator (e.g., an actuator 73 to be described below) for driving the rotation restricting mechanism is provided on an outer periphery of the differential gear casing of the differential gear system.
According to aspect (1), since the plurality of pinion gears only rotate without revolving, the operation of the entire power system can be stopped when only one of the pinion gears is connected to the rotation restricting mechanism.
In addition, since the rotation restricting mechanism is mechanically connected to the pinion gear, the force for maintaining the wheel, that is, the vehicle in the stop state can be small as compared with a case where the rotation restricting mechanism is connected to the differential gear casing of the differential gear system, and thus the actuator for driving the rotation restricting mechanism can also be reduced in size.
According to aspect (2), since the rotation restricting mechanism is mechanically connected to the one pinion gear located uppermost out of the plurality of pinion gears, it is possible to prevent intrusion of water into the actuator for driving the rotation restricting mechanism.
According to aspect (3), since the pinion gear includes the large diameter gear and the small diameter gear and the small diameter gear meshes with the second gear, enlargement in dimension in the radial direction can be prevented.
According to aspect (4), since the parking gear engaging with the rotation restricting mechanism is provided on the large diameter gear of the one pinion gear, the space of the outer periphery of the small diameter gear can be effectively utilized.
According to aspect (5), since the actuator for driving the rotation restricting mechanism is provided on the outer periphery of the differential gear casing of the differential gear system, the space of the outer periphery of the differential gear casing of the differential gear system can be effectively utilized.